A printed circuit board forms an essential part of an integrated circuit. The main benefit of using a PCB to assemble a circuit is that you don’t need to wire each board-mounted component. PCBs have integrated conductive pathways, typically copper strips on the base, which conduct the current between the various resistors, capacitors, diodes and transistors. For this reason, PCBs are particularly suitable for self-assembly kits, such as guitar effects pedals. If you are having trouble with the assembly process, troubleshoot your work. Instructions 2 Place the meter lead between the first and second component on the board. The first component is typically the one closest to where the power supply wire is connected to the board. 3 Note the reading. If that part is good, the reading will be within a five percent tolerance range of the advertised value. PCB components typically have the value printed on the side. For example, resistors have their value in ohms printed on the side. If the reading is outside this tolerance range, remove the part and replace with an identical one. If the reading is zero, the part is most likely shorted out. 4 Test the remaining components in the same way. Note that if one component is shorted out, the next component in the chain will most likely give a zero reading too. Visual Inspection 6 Unscrew the fully populated circuit board from the base of the circuit enclosure. Circuit boards are typically held in place with circuit board screws, calling for a small Phillips screwdriver. 7 Place the board face-down, so the conductive strip is exposed. To prevent damaging the board-mounted components, balance the PCB over the edge of two books to elevate the parts off your workbench. 8 Inspect the conductive pathways, using a magnifying lens. Look for cracks in the conductive pathways. In some circuits, the PCB conductor strips may be cut with a razor before assembly. This is to isolate parts of the circuit. If this is the case, and you inadvertently mount a board component between two breaks in the strip, the circuit won’t work. If you spot a crack in the conductive pathway, remove all of the parts from the board and use a different board. 9 Inspect the solder joints bonding the connector leads to the conductive pathways. If these are not correctly soldered in place, it may short out the circuit. Removing Bad Components 11 Press the hot tip of the iron against the solder joint fusing the connector leads of the component to the conductive pathway. Wait for the joint to cool. 12 Straighten the leads with a pair of tweezers. 13 Flip the board over and slide the component out of the board turret. By replacing that particular component with a brand new one, you can accurately determine whether the assembly problem is caused by a bad part or a bad PCB.
Testing
1 Set your multimeter to “Resistance.”
5 Disconnect the power supply. If the circuit is battery-powered, remove the battery and leave the battery snap wires intact. If it is mains-powered, melt the solder joint connecting the power supply wire to the board.
10 Turn on your soldering iron.
